Polymerization is the process of reacting monomers (molecules that can chemically bind to other molecules) together to form polymers—chains of repeating structural units. Polymerization is often executed to form thin films on various objects such as semiconductor wafers, flat panels, and other substrates. One conventional polymerization process involves using a process chamber to control chemistry and temperature to create a polymer surface covering on a given substrate.
In one conventional process, monomers of a given chemistry are applied to (or deposited on) a substrate. The monomers can be considered as a group of short molecular chains. After monomer application, a linker is introduced. This linker is also known as an initiator. The initiator functions to bring together or link the short molecular chains, thereby serving in a binding capacity. Thus, the initiator helps to form or create large or long molecular chains from the short molecular chains.
Polymers can be created having various different chain lengths and architectures. Additionally, physical and chemical properties of a given polymer can be a function of chain length. The polymer dispersion Index (PDI) is a metric that details the distribution of polymer chain lengths within a sample polymer. Accordingly, for certain applications, a relatively short chain length may be desired, while other applications call for polymer properties associated with polymers having relatively long chain lengths.